He was arrested for failing to show up for a summons. Same thing would happen in the US. If you were issued a summons for court, and decided not to show up, you would get an arrest warrant issued against you. If the Rabbi showed up and discussed his endorsement of the book, he would not have an arrest warrant right now. But this continues a trend in the ultra orthodox community of ignoring any law that they personally do not find just. By the way, for those who state that he is such a great Torah figure - at what point is such a giant liable under the law? If he were caught fondling young boys, should he not be arrested because he's a Torah scholar?
Three minors arrested in Jaffa for throwing rocks at a bus; no injuries reported (Haaretz)